2 Replies Latest reply: May 31, 2012 6:05 AM by Gernot Hoffmann RSS

    CMYK Colors and profiles

    ottz0 Community Member

      I am using PS CS4 and I am in CMYK, proof setup is working CMYK and the color settings I am using is U.S Web Coated (SWOP) v2.

       

      If I slect a color which is 100% black (greyscale) which is 0 C, 0 M, 0 Y, 100 K my color picker comes out at a muddy grey with a touch of red.

       

      Why is this? Otherwise I have selected 100, 100, 100, 100 and this is 100% black for CMYK

       

      Should I not worry about this?

       

      My output is CYMK digital print

        • 1. Re: CMYK Colors and profiles
          Mylenium CommunityMVP

          Your system is simply not color calibrated and thus all your efforts are going to waste. Your black appears grey because without suitable profiles, the on-screen simulation is off. And 4x100% is not black. It's almost physically impossible to print something with 400% ink saturation. Really, you need to read up on color management and requirements for print....

           

          Mylenium

          • 2. Re: CMYK Colors and profiles
            Gernot Hoffmann Community Member

            I've done the necessary tests:

             

            Image A: original RGB image, additionall a  square R=0,G=0,B=0

            sRGB

             

            Image B (not shown): Grayscale

            G=2.2

             

            Image C: CMYK image with Grayscale pasted into the K-channel. C,M,Y void.

            US.Web Coated (SWOP) v2

             

            This image looks a little washed out. The black square has K=100 and now

            (calculated from CMYK back to sRGB) R=35,G=31,B=32.

            Furtheron L=12,a=2,b=0. This black ink has indeed a weak red appearance,

            but that's hardly visible. The wash-out becomes even stronger for 'simulate

            black ink' and the appearance turns into sepia for 'simulate paper color'.

            It's well known that pure black ink doesn't create a pleasant black.

             

            By the way: It's not prohibited to print by 400% Total Ink Coverage.

            This is just the ultimate value for ink limit testpatterns for inkjets.

            Using excellent proofing paper, the ink does not bleed.

            But there are two reasons, why the ink limit is preferrably at 320% or

            below:

            a) with too much ink the print doesn't dry fast enough, which would be

            a desaster for offset printing.

            b) more ink doesn't necessarily mean darker. Adding yellow ink can

            make the printed black even lighter.

             

            Examples by Photoshop CS2

             

            Best regards --Gernot Hoffmann

             

            Edit: the images have the same pixel dimensions but are shown here

            by different sizes.

             

            Image A

             

            N-23082011-214-cropped.jpg

             

            Image B  (Grayscale) here not available

             

            ImageC  CMYK K-only

             

            N-23082011-214-cropped-gray-CMYK.jpg

             

            Message was edited by: Gernot Hoffmann